I overhear this conversation taking place where the customer wants something printed and for it to have a black background. So they ask for a black foam board but my co-worker tells them that you cannot print on a black foam board and that there's no "white ink" and that their image wouldn't show up.
The couple is completely lost here. My co-worker is explaining to them that you print on a white foam board and print the black background. But they think it "makes more sense" to print on black.
The lady walks around the shop and sees another print job that has white text on a black background. She mumbles "see, this is what I want... I don't get it..."